The proposed pilot research project will examine the empirical validity of key assumptions regarding the epidemiology of adolescent alcohol use that underlie current federal and state policies toward community- based prevention of alcohol use and other problem behaviors. Communities are faced with a diverse array of dozens of identified risk factors and a confusing array of alcohol and other drug (ATOD) prevention programs. To help provide a coordinated and planful community-based approach, policymakers have moved toward an emerging best practices model we term "Community Diagnosis" (C-Dx). In this model, communities systematically assess and identify risk factors that are elevated compared to national and state norms, and then select preventive interventions targeting those elevated risk factors. The C-Dx approach is being instantiated in communities through the policies of state and federal governments, as well as foundation initiatives. The C-Dx model is based on research showing that a large number of risk/protective factors are linked to adolescent alcohol and other substance use and abuse. However, in most cases to date, this linkage has only been made at the level of individuals, not communities. Such research provides a rationale for intervening to enhance parenting in individual families to reduce early- onset adolescent alcohol use. However, what has not yet been demonstrated is that these same relationships hold at the level of community, where decisions on actions are made. It is likely that individual-level epidemiology alone does not provide a sufficient basis for community prevention decisions;there is a need for in-depth exploration of "community level social epidemiology of youth risk and outcomes." There are at least five assumptions in the move from individual research to community prevention that have not been adequately examined and may not be valid. The five assumptions will be examined through quantitative analyses of several large datasets that contain data on youth risk and ATOD use across communities. The results of these analyses may enable us to recommend changes to the C-Dx model;however, it is likely that this pilot project will set the stage for a more intensive line of work examining the community epidemiology of alcohol and other substance use. PUBLIC HEALTH RELEVANCE: This project seeks to test five key assumptions in the application of individual epidemiology concerning adolescent alcohol use to community-level decision-making. The validity of these assumptions has not been demonstrated previously. If these assumptions are not valid, then the leading model for applying science to community-based prevention of alcohol and other problem behaviors may need to be reformulated to maximize the effectiveness of prevention resources. Increasing the efficiency of the application of prevention resources would have substantial public health benefits for youth, families, and society.